1. Field of the Invention
The present invention relates to an automatic charging apparatus employing a transformerless system which can be made small and light.
2. Description and Problems of the Related Art
Many conventional charging apparatuses for charging a battery employ a transformer system which lowers a commercial power source voltage to a charging voltage using a transformer.
However, in the case of charging a battery which outputs large current such as a power battery loaded on an electric automobile etc., the conventional transformer-system charging apparatus causes an inconvenience that it becomes large in size and heavy in weight since it requires a large-sized transformer.
In order to obviate such an inconvenience, for example, a transformerless-system automatic charging apparatus which does not use a transformer therein is proposed in the Japanese Patent Office Laid-Open Publication No. 49-4138 (the Japanese Patent Office Publication No. 52-35863).
The conventional automatic charging apparatus, however, causes inconvenience in that it is poor in charging efficiency since it is designed to charge a battery by on-off controlling a Silicon rectifier device using a voltage switching circuit composed of transistors so that it cannot charge a battery with a charging current best suited to the state of the battery even if it can be made small and light.
The present invention has been made to eliminate this inconvenience to provide an automatic charging apparatus capable of efficiently charging a battery with a charging current best suited to the state of the battery.